An image forming apparatus reads an image from a document, forms a developer image corresponding to the read image on paper and fixes the developer image on the paper using a fixing apparatus.
The fixing apparatus includes a heating roller and a pressure roller. The fixing apparatus catches the paper-sheet between the heating and pressure rollers and carries it to fix the developer image on the paper-sheet.
An induction heating type fixing apparatus contains a coil inside a heating roller. The coil is supplied with a high-frequency current and generates a high-frequency magnetic field. The high-frequency magnetic field causes an eddy current to be generated on the heating roller. Due to Joule heat based on the eddy current, the heating roller generates heat by itself.
The high-frequency current is generated from a high-frequency generation circuit (which is also called a switching circuit) that is connected to a commercial AC power supply via a rectifier circuit. The high-frequency generation circuit includes a resonance capacitor that forms a resonant circuit together with the coil and a switching element that excites the resonant circuit. The high-frequency current is generated from the output voltage (DC voltage) of the rectifier circuit.
The voltage level of the commercial AC power supply varies from area to area. For example, there are two areas whose voltage levels are 100 V and 200 V, respectively.
No images can properly be fixed if a 200-V fixing device is used in an area where the voltage of the commercial AC power supply is 100 V or if a 100-V fixing device is used in an area where the voltage of the commercial AC power supply is 200 V.
Consequently, two different fixing apparatus of 100 V and 200 V have to be designed and manufactured, which results in the increase in costs.